1. Technical Field
This invention generally relates to pneumatic tire molds and, more particularly, to the connection between the die ribs that form the tire tread pattern and the mold sections of a pneumatic tire mold. Specifically, the present invention discloses tire mold sections that each have at least one dovetailed groove that slidingly receives a plurality of dovetailed die ribs with the die ribs cooperating to form a continuous, 360 degree die when a plurality of mold sections are fit together to form a tire mold.
2. Background Information
Pneumatic tire molds must have inwardly-projecting continuous dies that form the continuous tire tread on a pneumatic tire during the molding process. These inwardly-projecting dies are formed by combining a plurality of die ribs that are each individually connected to a section of the tire mold. Although the exact number of die ribs and mold sections vary in specific applications, approximately nine mold sections and approximately seventy to seventy-five die ribs are used to form the continuous, 360 degree die in at least one example of a tire mold. A typical pneumatic tire uses three or four of these continuous dies to form the tread pattern of the tire.
Most tire tread patterns include repetitive elements that allow repetitive die ribs to be used to form the continuous, 360 degree tread die of the tire mold. The repetitive die ribs may be formed by any of a variety of molding methods or machining methods known in the art. One molding method that is used to form the die ribs is lost wax casting. Lost wax casting uses a wax representation of the final die rib that is coated with an appropriate material. The wax is melted out of the coating leaving a hollow mold. Although this method allows the intricate projections for the sipes and blades of the tread pattern to be formed on the die ribs, the method does not allow holes to be formed in the molded piece. Such holes have been used in the art to receive pins that connect the die ribs to the mold sections.
In prior art molds, the mold makers had to machine holes into each of the die ribs so that they could be connected to the mold sections. For a typical tire mold, the mold makers had to machine 210 to 300 of the die ribs as well as machining corresponding holes into the mold sections. One typical method of connecting the die ribs to the mold sections is depicted in FIG. 7. The configuration depicted in FIG. 7 includes a prior art die rib 10 connected to a prior art mold section 12. Mold section 12 is formed with a longitudinal rectangular shaped groove 14 into which the base 16 of die rib 10 is inserted. Various projections 18 that form the sipes and blades in the pneumatic tire tread pattern project from die rib 10 and are configured to abut the inner surface 20 of mold section 12. In the past, a machinist drilled a pair of holes 22 in mold section 12 that were configured to align with a pair of holes 24 that were drilled into die rib 10. A pair of pins 26 were then used to connect die rib 10 to mold section 12. Although this connection configuration is not overly complicated, it is time consuming when repeated on 210 to 300 die ribs. It is thus desired in the art to provide a die rib and mold section configuration that allows the die ribs to be quickly and easily connected to the mold sections without the machining steps.